04 July 2011

Rock Wind and Very Hot Air

The coldest winter I ever spent was a summer’s day in San Francisco. (Wrongly attributed to Mark Twain)

Hot air rises. If you think about hot air balloons, and sky lanterns, this phenomenon is easily understood.

From Redding all the way to Mexico is a desert. In summer time hot air rising (over the desert) sucks in cold air from the sea. Even before the Golden Gate Bridge was built, two mountain tops created the perfect funnel for cool air mass. Mount Tamalpais to the north, in Marin County and Twin Peaks, the top of San Francisco, direct this air towards Berkeley and up the delta while simultaneously squeezing the cool air mass as it passes the narrow channel between Fort Point and East Fort Baker. Squeezing is synonymous with condensing and therefore condensation, more locally known as fog.

June, July and August are not good for being a tourist in San Francisco. September and October, due to the lack of temperature gradient are far better times to view the incredible sights in The City. However, if you are into wind sports like sailing, para gliding, kite surfing, wind surfing, kite flying, hang gliding, etc. This is the time of year to blossom.

Wind travels in circles too. Picture the arms of a hurricane with “s” shaped patterns coming out from the eye. Sometimes you are able to work yourself up(north) or down(south) the beach to catch off-shore or on-shore winds. If you are a surfer, winds can help you or make your day more challenging. An offshore wind blows out to sea from the beach and holds up a wave when it breaks forming better curlers. It may also blow your kayak out to sea so pick your toys wisely today. An onshore wind blows from sea to beach and “blows down” a wave pushing it down instead of holding it up.

Gusty winds are more difficult to learn sports like windsurfing and kite boarding. You will want consistent winds of about 10mph. You will want a beginner board that is wide and long and a beginner sail that is small and light. Pack plenty of energy and hydration. The learning curve is pretty steep.

Winds can affect your touring kayak greatly and is often more dangerous than the cold water. Most people think that wind will turn your kayak into the wind or away from it. That is, so that you are either getting a face full of wind or the opposite, you are getting slapped squarely in the back between your shoulder blades with each gust. However, wind actually turns your kayak sideways to it. Wind will then be coming from directly left or right depending on which side of the boat the wind is on. At about 15mph you will want to be thinking about another plan as you will be spending some energy paddling against the wind that wants to turn you sideways to it. At 20mph you will want a rudder. (more on this on kayaking blog) At 25mph you will be seeing whitecaps where there is no current. The wind is actually picking up water and dragging it around with her. An astute paddler can see wind gusts do this over the surface of the water. Hint: if you see the windsurfers unfurling their sails, you might want to keep your kayak close to land. I can almost always expect the wind trying to push me back up river at the take out after a day of river paddling. It usually gets stronger until the sun goes down and then disappears quite rapidly with nightfall. Again, it is the remnants of hot air rising and the Delta Breeze

My learning how to surf blog has more information about beaches and wind.

Other stuff:

Hot springs are geothermal activity that happens in volcanic areas throughout the world. They are common in the Sierra Nevadas. Links Below.

The native American Indians knew about hot air rising and had built it into their teepees. They had very tall 18-25’ teepees. They would build a small fire in the middle, and then open up the bottom side vents causing a “venturi” effect.

If you go to the old Victorian homes in the southern states like Mississippi and Alabama you will notice the domes with the turret of windows up top. Then look lower, at the base of the dome, you will see gas jet nipples all around. If you ask a docent what they are for, they will tell you that they light them in the summer time, like the teepees, the hot air rising sucks cold air from the base level windows. The shrubbery around the base of the house is a source of cold air coupled with the morning dew that rests on the leaves, it creates a swamp cooler effect, through convection and evaporation.

Fort Funston:

Where hang gliders and para-gliders literally jump off a cliff and are swept up by the winds. It is also a very large dog park, for the large and not so large breeds and although has incredible expanses of beaches, rarely do people make the 10 minute walk down to the beach.

Head North to Novato or West to Walnut Creek:

Almost always where the fog stops and the sunshine persists. Fog is always in battle with the sun as evaporation and higher in-land temperatures will ultimately be the cloud’s demise

Delta Breeze:

The after effect of strong fog is a back lash. It is the after effect from the fog and winds caused by the hot air rising. The Delta Breeze often rolls in during early evening times here in Sacramento becoming the welcome rescue from very hot days. I always recommend spending your days in coastal or river waters or up at cooler elevations and heading back to the valley for an evening in the garden or patio.

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The coldest winter I ever spent was a summer’s day in San Francisco. (Wrongly attributed to Mark Twain)

After the summer solstice sunlight begins to diminish. So plan your trips now! It is your last chance before winter time hits and you will have not ventured much.

Do your own youtube or google searches on these:

Concerts in the park, dive in movies, swimming pools and swimming holes, escape the heat. Remember these are just starters for your imaginary pleasure. There are so many things out there to do. Get out there!

Today Roz is a little over two months out at sea, alone and self supported she continues to battle rogue waves and equipment issues. I started this blog so that you may support her in her mission to spread awareness and continue to do small actions to reverse some of the ecological blights we have unleashed onto the world. Here is a quick link to help me out. All you have to do is put www.RozSavage.com in the comment section. Thanks, it is worth a go!

2 comments:

The air closest to the earth is warmest. (solar radiation and density, think snow on mountain tops and hot asphault parking lots and streets)

Hot air rises; picture a hot air balloon or sky lanterns

As it climbs to altitude, it gets colder and loses density and drops back down. This is the way it is supposed to happen. In meteorological terms this is "unstable" and a good thing.

What you don't want is "stable" air masses.That almost always means the existance of a temperature inversion layer.

Warm air for some reason (usually density) does not cool off and instead forms a cap on the cool air below. (this is relative only to the two distinct layers and the "cooler", lower layer may atually be quite warm to down right hot. While trapping that cooler air may seem beneficial at first, in reality what is really getting trapped is energy. This energy can be released as many adverse conditions including hail, thunder storms, ice storms, tornadoes, hurricanes, ground level air temperature becomes too hot or unseasonably cold. Also, since this happens most notably in cities(most cities are built near water source), we notice the air pollution that persists instead of blowing away to another part of the planet. Stable air masses may be a warning of adverse weather ahead.

Two versionsThe two most common versions are when cold air comes down a mountain side, breaks through the warm air cap and gets stuck under the warm air.

Coastal waters can cool the air directly above it and that cool air can get trapped under warmer air above. The whole system, warm and cool air move over the land mass as a "marine layer".

Many other versions exist but the two above are the more common reasons we have an inversion layer formation here in Sacramento Valley.

Today Roz is a little over two months out at sea, alone and self supported she continues to battle rogue waves and equipment issues. I started this blog so that you may support her in her mission to spread awareness and continue to do small actions to reverse some of the ecological blights we have unleashed onto the world. Here is a quick link to help me out. All you have to do is put www.RozSavage.com in the comment section. Thanks, it is worth a go!